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Gut Microbiome, Immunity and Respiratory Infections

By March 27, 2020 2 Comments
Mar 27
Gut Microbiome, Immunity and Respiratory Infections

The coronavirus pandemic has us all casting around for ways to help protect ourselves and others from this respiratory infection. We are all aware of social distancing and other government legislation and advice. However, every little bit helps and with this in mind you may wish to consider whether your gut microbiome can help protect you too.

Dysfunction of the gut microbiome is now believed to be involved in the pathogenesis of not only certain gastro-intestinal diseases but also neurologic, rheumatologic, metabolic and hepatic disorders.

The gut microbiome interacts with and alters the function of many other parts of the body including the brain and cardiovascular system. There are also interesting linkages such as the use of prebiotics and probiotics in the treatment and prevention of atopic dermatitis.

Importantly these days there is increasing evidence of the linkages between the gut microbiome and the bodies’ immune system.

The beneficial effects of faecal transfer and reduction in the recurrence of gastro-intestinal Clostridium difficile infections are well documented. So too is the evidence for the role of the gut microbiome in other gastro-intestinal conditions such as inflammatory bowel disease.

However, in the current pandemic is there evidence that diet and the gut microbiome can influence the effectiveness of the immune system?

Intuitively one knows that a healthy diet should help keep one healthy and help maintain a well-functioning immune system. But is there any more specific information about the gut microbiome and the immune system and any evidence that changing the gut microbiome can boost your resistance to respiratory infections?

There are several lines of evidence:

  • Effect of probiotics on the incidence of respiratory tract infections (RTI)
  • Effect of prebiotics on the incidence of RTI
  • Observations on the relationship between the make-up of the gut microbiome and the response to RTI.

There is good evidence that probiotics can improve in vivo and ex vivo measures of immune function in older adults.

Similarly, a meta-analysis (combining separate trials and analysing the combined data set) concluded that probiotic consumption decreases the incidence of RTI in children (Wang, Y et al, Medicine (2016) volume 95 pages 31-43). The trials included both prevention trials and treatment trials and used both single probiotic strains and mixtures of probiotics. The meta-analysis used 23 identified studies involving 6269 children.

Another review reported on two additional studies that showed a reduction in the incidence of various RTI in children who consumed specific probiotics. Variously reductions in the incidences of otitis media, lower respiratory tract infections and upper respiratory tract infections occurred.

Infants who received formula supplemented with a mixture of fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS) for the first six months of life had a reduced risk of recurrent respiratory infections and a reduced risk for upper respiratory tract infections (Arslanoglu, S. et al, J. Nutrition (2007) volume 137 pages 2420-24240).

Data on prebiotics and RTI are sparse.

However, there are a few studies in athletes (Colbey C. et al Sports Medicine (2018) volume 48 pages S65 to S77).  Upper respiratory symptoms (URS) are the most common illness in athletes. URS includes coughing, sneezing, congestion, sore throat and the like and is thought to affect performance.

One study administered beta glucan for 28 days to 182 healthy adults before a marathon found a 37% reduction in URS symptom days compared to placebo.

In mice it was shown that the gut microbiome is associated with the productive immune response in lungs involving virus specific T cells in response to influenza A virus infection

(Ichinobe T. et al, Proceedings of National Academy (2011) volume 108 pages 5354-5359).

These beneficial immune effects outside of the gut are thought to be mediated by a common mucosal immune system; that immune effects activated in the gut are also reproduced in the lung mucosa.

There are already many good reasons for paying attention to your gut microbiome and the evidence linking the gut microbiome with protection against respiratory infections is yet one more.

And when a coronavirus vaccine is available it is known that a well-functioning gut microbiome will improve vaccine efficacy (Vlasova A.N. et al, Current Opinions in Virology (2019) volume 37, pages 16-25).

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